Why does red shift provide evidence that the universe is expanding

It is a result of the space between the Earth and the galaxies expanding. This expansion stretches out the light waves during their journey to us, shifting them towards the red end of the spectrum. The more red-shifted the light from a galaxy is, the faster the galaxy is moving away from Earth.

Red-shift Emission spectra Light from a star does not contain all the wavelengths of the electromagnetic spectrum. Spectra from distant galaxies Astronomers can observe light from distant galaxies. Random Question. A line drawn perpendicular to a line through the tips of the horns of the crescent moon doesn't point to the Sun!

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As this is towards the red end of the spectrum, astronomers call it redshift. The degree of shift can also give astronomers information about how fast the object is moving relative to us. A faster-moving object has a greater shift in wavelength. Using various measures to establish how far away the galaxies were, Edwin Hubble and those that followed him found that their velocity was always proportional to their distance. But is the expansion rate really constant? How do astronomers know the universe is expanding?

The Doppler effect The noise of a siren or a car speeding past sounds higher in pitch the closer it gets to you and lower as it moves away.